sign in sign up
<<
Home , Bird feeding, Butorides, Cattle egret, Egret, Great egret, Green heron

U.S. Department of Agriculture & Plant Health Inspection Service Services August 2017 and Wildlife Damage Management Technical Series

Michael D. Hoy District Supervisor USDA-APHIS-Wildlife Services Almyra, Arkansas

Figure 1. Great Blue ( herodias)

Human-Wildlife Conflicts

Landscapes -eating also can have an impact on intensively managed sport fisheries. Herons and egrets commonly cause Damage occurs when herons and egrets Quick Links damage at aquaculture facilities and feed on fish purchased and released for Human-Wildlife Conflicts 1 recreational fishing waters where fish are recreational sport fishing activities. Values held at high densities. In one study, on of these fish can be quite high given the Damage Identification 2 average wading birds consumed from 4 to intensity of management activities and the Management Methods 2 24 golden shiners per day at minnow direct relationship of fishery quality to Economics 4 production facilities in Arkansas. Great property value. blue herons and great egrets commonly Overview 5 feed at catfish production facilities in Livestock and Pets Legal Status 9 Mississippi. The tendency for herons and egrets to congregate in large feeding Great blue herons are known to feed on Glossary & Key Words 10 flocks often leads to extensive loss of fish fish in backyard water gardens. This can be a problem in urban areas as fish in Resources 11 at aquaculture facilities. these small ponds often are considered Appendix 12 valuable pets. Page 2 WDM Technical Series─Herons and Egrets

Management Methods

Integration of multiple control methods is essential in developing a strategy to manage heron and damage. If implemented in a timely and persistent manner, all methods discussed below will provide effective control of wading damage. Reliance on one method rarely works to prevent or control extensive bird damage. When developing a control program, realize that every damage situation is unique. Incorporate the uniqueness of the situation into your control program and use as many control strategies as possible to develop your management Figure 2. damage to fish. strategy.

Habitat Modification Human Health and Safety Small, shallow impoundments are attractive feeding sites Nesting colonies often cause problems in urban areas for wading birds and should be avoided. Herons and egrets when urbanization spreads into lowland where will rapidly congregate if fish are left in these conditions for colonial nest sites have traditionally existed. Odor from extended periods. Shallow water conditions are often deposited fecal material in these areas is a problem. necessary to harvest commercial fish and cannot be Histoplasmosis is not commonly found in soils from heron/ avoided. If this occurs, be prepared to implement egret rookeries, but proper conditions for this fungal frightening devices to disperse the birds. disease exist in these areas. Rookeries near airports may pose a flight safety risk to aircraft. Diseased fish are highly vulnerable to heron and egret depredation. Maintain quality fish health standards to help minimize wading bird depredation.

Damage Identification

Often, heron and egret damage initially is identified by the presence of birds feeding at the damage site. Further investigation will determine that fish are missing or damaged (Figure 2). Damage often includes puncture holes or slices on the back or sides of a fish.

Occasionally, damage at aquaculture facilities is not realized until harvest when fish production falls short of expectations. This is often the case if ponds are not regularly frequented by humans or if birds are feeding at night.

Figure 3. Herons and egrets prefer vegetated banks. U.S. Department of Agriculture Page 3

Herons and egrets prefer to feed along vegetated banks A where they are concealed from their prey (Figure 3). Pond banks without vegetation are less attractive to birds and will decrease the efficiency of wading .

Urban rookeries can be prevented by adequately thinning nesting . Since herons and egrets are protected under the Migratory Bird Treaty Act, habitat management in active rookeries is prohibited. All habitat modifications to prevent future rookeries must be performed during the nonbreeding season. In some situations, it is possible to get a Migratory Bird Depredation Permit from the U.S. Fish and Wildlife Service (USFWS) to allow habitat modifications during the breeding season. Contact your local USFWS office for further guidance. B

Exclusion

Total exclusion is the complete enclosure of an area with netting or wire mesh caging to eliminate bird use (Figure 4). Exclosures are the only way to completely restrict heron and egret access to ponds and raceways. It is effective, but due to cost and structural problems in spanning large distances, it is generally considered impractical to totally exclude birds at water holding structures larger than 5 acres. In addition, exclosures are difficult to incorporate Figure 4. A total exclosure eliminates access by birds completely (a), into a commercial aquaculture facility as they can interfere whereas overhead lines or wires provide only partial exclusion (b). with fish management practices.

Total exclosures are recommended for protection of fish in urban water gardens. The small ponds and high value fish make this control method cost effective. However, the Overhead wire exclosures are easier to incorporate with exclusion system may be aesthetically unacceptable to the fish management practices and are easier to maintain landowner. than complete enclosures. Overhead wire systems are considered cost effective for small ponds (less than 5 Partial exclusion is the limited enclosure of an area with acres). It is recommended that high-value fish subject to wire or string lines to discourage bird use (Figure 4). The by herons and egrets be raised in small ponds lines are run laterally or set in a grid pattern across ponds with overhead wire systems. or raceways to impede access by birds. Partial exclusion is usually less expensive than total exclosure, but will not All exclusion systems must be structurally sufficient to eliminate heron and egret use of the site. As with total withstand the weight and impact of birds. Consider exclusion, overhead wire systems are impractical for large weather conditions; the infrastructure should be strong ponds due to the difficulty in spanning large distances. enough to support accumulations of ice and snow.

Page 4 WDM Technical Series─Herons and Egrets

Perimeter fencing and wires have been used with limited Trapping success to exclude herons and egrets from ponds. Wading birds quickly acclimate to barriers and jump over wires to Allowed with permits, but typically ineffective at controlling feed on fish. Electric perimeter wires also have proven to damage. be ineffective and impractical for most situations. Shooting Frightening Devices It is illegal to shoot herons and egrets without a permit Frightening devices are effective tools for dispersing large from the USFWS. A permit can be obtained by commercial concentrations of herons and egrets from damage sites. fish farms to augment their on-going nonlethal harassment Many visual and noise-making devices are commercially programs. Contact USDA APHIS Wildlife Services or your available for scaring birds, including gas-operated state wildlife agency for more information. exploders, pyrotechnics, electronic noise makers, bird distress calls, effigies, eyespot balloons (Figure 5), reflective tape, and water spray devices. Methods for incorporating these devices into a bird scaring program are Economics described in the Bird Dispersal Techniques publication of the Wildlife Damage Management Technical Series. As Heron and egret damage is difficult to quantify. The relative discussed previously, it is important to use a variety of abundance of fish among aquaculture ponds is highly frightening devices in a timely and persistent manner. variable. Therefore, it is difficult to assess the overall impact of bird depredation until harvest. At large aquaculture facilities, the effectiveness of these devices is compromised over time as herons and egrets Loss estimation requires knowledge of the number of birds become habituated to the deterrents. At this point, present, feeding duration, number of fish taken, and the frightening devices will simply push herons and egrets from crop value. One study assessed esophageal and stomach one pond to another nearby pond where they will continue contents of 4 species of herons in Arkansas and found feeding. Lethal control may be necessary to enhance the losses of golden shiners ranged from $0.10 to $0.62 per overall effectiveness of a bird scaring program at these feeding. Based on 2 feedings per day, a flock of 100 sites. See the Shooting section for more details. wading birds present on a fish farm for a 3-month period

At urban rookeries, frightening devices can be used to relocate birds prior to nesting. Once active nests are established, it is illegal to intentionally disperse birds from a nest site. Contact the USFWS for further clarification.

Repellents

None are registered.

Fertility Control

None are available.

Figure 5. “Eye-spot” balloons may help protect small areas from heron and Toxicants egret damage for a limited period of time.

None are registered. U.S. Department of Agriculture Page 5

resulted in losses from $1,800 to $11,160, depending on the species composition.

Indirect economic impact can occur when herons carry unwanted fish and vegetation into the aquaculture facility. Cross contamination of fish from nearby ponds can lead to unwanted polyculture and decreased crop values. Birds also have been implicated in the spread of fish diseases between pond complexes.

Species Overview Figure 6. walking through water.

Identification

Herons and egrets are freshwater or coastal birds of the family Ardeidae. The most common species include:

 Great blue heron (Ardea herodias)  Great egret (Casmerodius albus)  ( thula)  (Egretta caerulea)  egret ( )  ( virescens)  Black-crowned night-heron ( nycticorax)  Yellow-crowned night-heron (Nycticorax violaceus) Figure 7. Snowy egret with characteristic yellow feet.

Little blue herons (Figure 8) are similar in size to snowy Physical Description egrets, but blue grey with a maroon neck. Immature little blue herons are dusky white with dull green legs. Herons and egrets are medium to large sized birds with characteristic long legs, necks, and pointed bills. Legs are Cattle egrets (Figure 9) are slightly smaller than snowy extended and heads retracted during flight. They are egrets and are white with yellow bills and dark yellow or sexually monomorphic and typically colonial nesters. The coral legs. great blue heron (Figure 1) is approximately 4 feet tall with blue-grey and weighs between 5 and 6 pounds. Green-backed herons (Figure 10) are approximately 28 inches tall, with a blue-green back and chestnut neck. Great egrets (Figure 6) are slightly smaller than great blue herons and are white with black legs. Night-herons are similar in size to snowy egrets but grey, short-legged and thick-billed. Black-crowned night-herons Snowy egrets (Figure 7) are approximately 27 inches tall have a black back and neck (Figure 11). and are white with black bills and legs and characteristic yellow feet. Yellow-crowned night-herons (Figure 12) are similar to black-crowned, but have a white cap and cheek patch. Page 6 WDM Technical Series─Herons and Egrets

Figure 10. Green-backed heron.

Figure 8. Little blue heron.

Figure 11. Black-crowned in water.

Figure 9. .

Figure 12. Yellow-crowned night heron showing white cheek patch and cap. U.S. Department of Agriculture Page 7

Range roosts. For sign associated with aquaculture damage, see section on Damage Identification. The great blue heron can be found in areas across most of the U.S. and lower (Figure 13). The great Voice and Sounds egret occurs along coastal U.S. with many wintering areas in South and (Figure 14). The cattle egret Herons and egrets have distinctive vocalizations, but these appeared in in the 1950s; by the 1990s, it generally are not beneficial for identification. The most had become common in many regions. For range common sounds associated with great blue herons are information on other species, please see The Birds of squeaking roh-roh-rohs when landing or a series of North America Online. clucking go-go-gos building to a rapid frawnk squawk. Great egrets make dry, croaking sounds, nasal squeals and Tracks and Sign other harsh calls. For vocalizations of other species, please see The Birds of North America Online. Herons and egrets are most frequently identified by sightings near water or concentrations at communal

Figure 13. Breeding, non-breeding, and year-round ranges of the Figure 14. Distribution of great egret. great blue heron. Page 8 WDM Technical Series─Herons and Egrets

Reproduction native North American herons and egrets, which generally feed in or along water and not in close association with The size of the clutch, length of incubation, and age at livestock.” which birds reach sexual maturity varies by species. Great blue herons breed from March to May in the northern part Behavior of their range. Females lay 3 to 6 after mating. Those living farther north have the higher clutch sizes. Both sexes Foraging habits vary by species, but herons and egrets incubate the eggs, which hatch after 26 to 30 days. typically wade in shallow water in pursuit of prey. Feeding Parents feed the young by regurgitating food at the nest. by hovering and diving by these species has been observed The young fledge about 2 months after hatching and are when fish are concentrated in deep, open water. Great sexually mature at about 22 months. Great egret females blue herons are known to herd minnows toward shallows lay 3 to 4 eggs after mating. Both sexes incubate the eggs, of aquaculture ponds to increase foraging efficiency. which hatch in about 24 days. The young fledge about 2 to 3 weeks after hatching and can reproduce after 2 years. Herons and egrets are diurnal sight feeders that return to For information on other species, please see The Birds of roost at dusk. They will feed at night with favorable North America Online. moonlight or when disturbed from feeding during the day. Night-herons are the exception, as they prefer to feed at Mortality night and roost during the day.

Great blue herons commonly live more than 15 years and Herons and egrets are known to congregate in large flocks occasionally 24 years or more in the wild. More than half of when fish are concentrated in shallow water. the great blue herons born in any given year die before they are a year old. Great egrets have similar lifespans and Species in the Family Ardeidae are typically colonial mortality rates. For information on other species, please nesters. Their rookeries are often found in densely see The Birds of North America Online. vegetated, lowland habitats or wetland areas.

Population Status

The great blue heron and great egret suffered from heavy hunting pressure in the late 1800s and early 1900s for their breeding plumes. That, along with habitat loss due to drainage of , had a negative impact on their populations. According to the North American Breeding Bird Survey, populations of great egrets increased significantly from 1966 to 2010 in the U.S. The little blue heron, cattle egret, and green heron showed declines in population over the same years. For information on other species, please see The Birds of North America Online.

Habitat

Varies by species, but all are associated with wetlands throughout their life history. According to the Birds of North Figure 15. Great blue heron eating a fish. America online, the cattle egret’s preference for “lawns, fields, pastures and is quite unlike other U.S. Department of Agriculture Page 9

Food Habits

Herons and egrets discussed in this section are all piscivorous (Figure 15). They are opportunistic feeders, however, and will consume small , , and . Due to these food preferences, herons and egrets are attracted to shallow lakes and human-made impoundments.

Legal Status

Native bird species are covered under the Migratory Bird Treaty Act (MBTA) and given federal protection. Depredation permits can be obtained through the U.S. Fish and Wildlife Service. In addition, individual states may require their own permits for legal take of these bird species. Page 10 WDM Technical Series─Herons and Egrets

Acknowledgements

Figure 1. Photo by Robert Burton, USFWS Figure 2. Photo by USDA Figure 3, 6 and 8. Photos by Steve Hillebrand, USFWS Figure 4. Images from 1994 Prevention and Control of Wildlife Damage Figure 5. Photo by John Humphreys, USDA-APHIS-WS Figure 7. Photo by Jama Beasley, USFWS Figure 9 and 10. Photos by Lee Karney, USFWS Figure 11. Photo by Erni, Shutterstock.com Figure 12. Photo by Mark Musselman, National Audubon Society and USFWS Figures 13 and 14. Maps from The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of . Figure 15. Photo by Don Mammoser, Shutterstock.com

Portions of Prevention and Control of Wildlife Damage, 1994, Bird Damage at Aquaculture Facilities by W. Paul Gorenzal, Fred S. Conte, and Terrell P. Salmon were used in development of this publication. Special thanks to Thurman Booth, Brian Dorr, Harris Glass, Kris Godwin and Michael Kearby for their critical review.

Glossary Disclaimer

Piscivore: An animal that feeds on fish. Wildlife can threaten the health and safety of you and others in the area. Use of damage prevention and control Polyculture: The simultaneous cultivation of several crops methods also may pose risks to humans, pets, livestock, or kinds of animals. other non-target animals, and the environment. Be aware Rookery: A colony of breeding birds; the nesting place of of the risks and take steps to reduce or eliminate those birds. For herons, it may be called a heronry. risks. Sexual Monomorphism: The males and females of a Some methods mentioned in this document may not be species show no differences in coloration, size or body legal, permitted, or appropriate in your area. Read and structure other than their genitalia. follow all label recommendations and local requirements. Check with personnel from your state wildlife agency and local officials to determine if methods are acceptable and allowed. Key Words Mention of any products, trademarks, or brand names does not constitute endorsement, nor does omission Aquaculture, Ardea herodias, Casmerodius albus, Egret, constitute criticism. Fish predation, Heron Citation

Hoy, M.D. 2017. Herons and Egrets. Wildlife Damage Management Technical Series. USDA, APHIS, WS National Wildlife Research Center. Fort Collins, Colorado. 12p. U.S. Department of Agriculture Page 11

Resources Glahn, J.F., D.S. Reinhold, and P. Smith. 1999. Wading bird depredations on channel catfish (Ictalurus punctatus) in northwest Mississippi. J. World Aquaculture Soc. 30:107-114.

Hoy, M.D., J.W. Jones, and A.E. Bivings. 1989. Economic impact and control of wading birds at Arkansas minnow ponds. Eastern Wildl. Damage Control Conf. 4:109-112.

Hoy, M.D. 1994. Depredations by herons and egrets at bait fish farms in Arkansas. Aquaculture 20:52-56.

Krebs, J.R., and B. . 1973. Significance of head tilting in the great blue heron. Nature 242:533-535.

Kushlan, J.A. 1976. Wading bird predation in a seasonally fluctuating pond. Au. 93:464-476.

Kushlan, J.A. 1978. Feeding ecology of wading birds. Pages 249-297 in A. Sprunt, J.C. Ogden, and S. Winckler, eds. Wading birds. Rep. No.7. Natl. Audubon Soc., New York.

McCrimmon, Jr., Donald A., John C. Ogden and G. Thomas Bancroft. 2011. Great Egret (Ardea alba), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; accessed Sept. 17, 2015 from the Birds of North America Online at: http://bna.birds.cornell.edu/bna/species/570

Telfair II, Raymond C. 2006. Cattle Egret (Bubulcus ibis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; accessed Sept. 17, 2015 from the Birds of North America Online at http://bna.birds.cornell.edu/ bna/species/113

Vennesland, Ross G. and Robert W. Butler. 2011. Great Blue Heron (Ardea herodias), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; accessed Sept. 17, 2015 from the Birds of North America Online at http://bna.birds.cornell.edu/bna/species/025

Internet Center for Wildlife Damage Management (http://icwdm.org)

National Wildlife Control Training Program (http://wildlifecontroltraining.com)

The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology Page 12 Appendix

Damage Management Methods for Herons and Egrets

Type of Control Available Management Options

Total exclosures are recommended for protection of fish in urban water gardens. Exclusion   Overhead wires are more practical for larger areas.

Fertility Control None available.

Frightening Devices  Propane cannons, pyrotechnics, and other noise making devices.  Various visual devices effective on small ponds including flash tape, mylar balloons, scarecrows and effigies.  Distress calls generally ineffective.

Habitat Modification  Maintain water depth, promote steep pond banks, and eliminate vegetation at waterline at aquaculture facilities.  Thin vegetation at roost sites.

Repellents None registered.

Shooting Allowed with proper Federal and State permits.

Toxicants None registered.

Trapping Allowed with proper permits, but generally not effective for controlling damage.